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Abstract

Two successful recipes to enhance the thermoelectric performance,} namely carrier concentration optimization and reduction of thermal conductivity{,} have been combined and applied to the p-type (Ti/Zr/Hf)CoSb1-xSnx system. An intrinsic micrometer-scale phase separation increases the phonon scattering and reduces the lattice thermal conductivity. A substitution of 15 Sb by Sn optimizes the electronic properties. Starting from this{,} further improvement of the thermoelectric properties has been achieved by a fine tuning of the Ti to Hf ratio. The microstructuring of the samples was studied in detail with high-resolution synchrotron powder X-ray diffraction and element mapping electron microscopy. Linking the structural with the thermoelectric properties{,} a record thermoelectric figure of merit for p-type half-Heusler compounds of ZT [approximate] 1.2 at 710 [degree]C in Ti0.25Hf0.75CoSb0.85Sn0.15 was achieved. The phase separation approach can form a significant alternative to nanostructuring processing{,} saving time{, energy consumption and increasing the thermoelectric efficiency.